Measurements of materials being dispensed is known in the art. For example, magnets and Hall effect sensors have been used to indicate qualitative dispensing. For example, medication compliance monitoring is shown in US 2003/0089733 A1, dispensing of a predetermined volume of liquid is shown in GB2087839 A, U.S. Pat. No. 4,934,566 shows portion monitoring based upon a slidable control stem, and U.S. Pat. No. 6,360,181 B1 shows toilet tissue usage data collection. Generally, these references rely upon the proximity of the Hall effect sensor and magnet to indicate a change in state or in component operating position. Such a change is then related to the amount of material dispensed.
However, none of these attempts deals with the problems which occur when the amount of material being dispensed changes as a function of time and usage of that dispenser. For example, a pressurized container, such as one containing propellant dispensed air freshener, will dispense less material as depletion of the propellant occurs, due to less pressurization of the material to be subsequently dispensed. Further, a long continuous burst of dispensing will release a different amount of product than several quick bursts having the same cumulative dispensing time.
Additionally, when using a pump-type dispenser, such as a squeeze trigger liquid fabric refresher, partial pulls of the trigger will typically result in only partial dispensing of the pump charge. This causes less material to be dispensed, dependent upon the trigger stroke.
However, accurate measurement of material to be dispensed requires the factors be considered. Furthermore, the measurement should occur in a matter not readily detectable to the user or which does not interfere with normal usage patterns.